01 - In a large mixing bowl, combine the yogurt, lemon juice, ginger-garlic paste, tandoori masala, cumin, coriander, turmeric, chili powder, smoked paprika, vegetable oil, salt, and black pepper. Whisk until smooth and well blended.
02 - Add the chicken cubes to the marinade, tossing to coat every piece evenly. Cover the bowl with plastic wrap and refrigerate for at least 4 hours, preferably overnight, to allow the flavors to penetrate deeply.
03 - If using wooden skewers, submerge them in water for at least 30 minutes to prevent them from burning on the grill.
04 - Remove the chicken from the refrigerator and thread the cubes onto skewers, leaving a small gap between pieces. Alternate with onion slices and bell pepper pieces if desired.
05 - Preheat an outdoor grill, grill pan, or oven broiler to medium-high heat, approximately 400°F.
06 - Place the skewers on the hot grill and cook for 15 to 20 minutes, turning every 4 to 5 minutes and basting generously with melted butter or ghee. Cook until the chicken is charred at the edges and reaches an internal temperature of 165°F.
07 - Remove the skewers from the grill, sprinkle with fresh chopped cilantro, and serve immediately with lemon wedges alongside naan, rice, mint chutney, or raita.